The invention discloses a flame retardant, a flame-retardant corrugated board, preparation methods of the flame retardant and the flame-retardant corrugated board, and preparation equipment of the flame-retardant corrugated board. The flame retardant comprises dissolvent, ammonium polyphosphate, magnesium-aluminum hydrotalcite, aluminum hydroxide, a dispersant, adhesive and fatty alcohol-polyoxyethylene ether with the percentage by weight of 100 : (10-25) : (15-30) : (10-25) : (1-3) : (5-10) : (1-2); the corrugated board comprises a flame retardant layer, a surface paper layer, a ceramic fiber paper layer, a flame retardant layer, a corrugating medium paper layer, a flame retardant layer, a ceramic fiber paper layer, an inner paper layer and a flame retardant layer from the upper part to the lower part in sequence, wherein the flame retardant layer is formed by drying the flame retardant. The flame-retardant corrugated board has the advantage that burning of paper can be effectively prevented, and has good strength and cushioning performance.